Quote Originally Posted by QwertyMIDX
Because the RTW definition of mercenaries and the one being used when the Gaesatae are mentioned are pretty different. In RTW a merc can be hired by absolutely anyone, in the ancient world there were plenty of mercs who were a bit more picky about their employers, the Gaesatae were one of these.
True.

The Tindanotae ("Galatian Gaesatae") though weren't that picky.